This invention relates to a comonomer composition of an aromatic polycyanate and an aromatic monocyanate, and polytriazines derived therefrom. More specifically, it relates to these compositions when the aromatic monocyanate is substituted at each position ortho to the cyanate group.
Polycyanate monomers are well-known thermosets that polymerize to form polytriazines. Polytriazines possess good heat resistance, hardness, electrical properties, dimensional stability, corrosion resistance, and chemical resistance. They are useful as adhesives and as coatings for substrates. They are also useful for the preparation of advanced composites and for the preparation of electrical laminates.
Attempts have been made to enhance the physical properties of polytriazines by incorporating various phenyl monocyanates into aromatic polycyanates before cure. For example, phenyl cyanate and phenyl cyanate substituted at the para position have been used as comonomers to modify polytriazines prepared from aromatic polycyanates. Korshak et al., Polymer Science USSR, A17: No. 1, p. 23-27, 1975, disclose modified physical and mechanical properties of a polytriazine prepared from the dicyanate of bisphenol A and varying amounts of phenyl cyanate. This polytriazine is believed to be represented by the formula: ##STR1## Brand et al., NASA Contractor Report 3185, 1979, disclose reduced water sorption of polytriazines prepared from dioyanates and varying amounts of either 4-nonylphenyl cyanate or 4-phenylphenyl cyanate.
Unfortunately, even though the addition of the phenyl cyanates employed in the art reduces water sorption of the prepared polytriazine, other physical and mechanical properties of the polytriazine are adversely affected. Most significantly, Korshak et al., supra, disclose a significant reduction in toughness, as measured by impact strength, relative to a polytriazine prepared without the addition of a phenyl cyanate.
In view of the deficiencies of the prior art, a polytriazine with enhanced physical properties derived from a comonomer composition of an aromatic polycyanate and an aromatic monocyanate is needed. More particularly, a polytriazine derived from such a comonomer composition with increased toughness and overall outstanding physical properties is needed.